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Incubation of human articular chondrocytes with interleukin 113 results in the time-dependent expression of nitric oxide (NO) synthase. We report here the isolation of a cDNA clone which encodes a protein of 1153 amino acids with a molecular mass of 131,213 Da and a calculated isoelectric point of 7.9. CHO cells transfected with a plasmid harboring this cDNA clone expressed NO synthase activity that was inhibited by some L-arginine analogues. The deduced amino acid sequence of the human chondrocyte inducible NO synthase shows 51% identity and 68% similarity with the endothelial NO synthase and 54% identity and 70% similarity with the neuronal NO synthase. The similarity (88%) between the human chondrocyte NO synthase cDNA sequence and that reported for the murine macrophage suggests that the inducible class of enzyme is conserved between different cell types and across species.The synthesis of nitric oxide (NO) from L-arginine is now recognized as an important pathway for regulating the function of a wide variety of cells and tissues. NO exerts many of these effects through activation of the soluble guanylate cyclase (1). In the vessel wall, NO is synthesized by the vascular endothelium, to regulate smooth muscle tone and thus blood pressure (2-7). NO synthase is also present in the central nervous system, where NO is a neurotransmitter/ neuromodulator mediating the action of glutamate on N-methyl-D-aspartate receptors (8-11) and mediating/ modulating transmission in nerves previously recognized as nonadrenergic and noncholinergic (12). NO can also act as an autocrine regulator of some cells, including platelets, where it modulates their activation (13).NO generated by activated macrophages is also an important effector molecule in host defense, through a mechanism involving its interaction with iron-sulfur-centered enzymes (14) and/or superoxide anions (15). In this role, NO has been shown to possess antitumor (16) and antimicrobial activity against various parasites in vitro (17) and in vivo (18).NO is synthesized from L-arginine by the action of NO synthase(s), generating citrulline as a co-product. These enzymes are all NADPH-, FAD-, FMN-, and tetrahydrobiopterin-dependent (19). Both the neuronal and inducible NO synthases are P450-type heme proteins (20). In addition to control at the enzyme level, NO synthesis can also be regulated through the expression of different enzymes in various cell types. In endothelial cells (21,22) and neuronal (9, 10) and other (13, 23, 24) tissues, NO synthase activity is constitutively expressed and has a requirement for Ca2+ and calmodulin (22). In contrast, NO synthase is synthesized de novo in macrophages, hepatocytes, Kupffer cells, vascular smooth muscle, and vascular endothelium following activation with endotoxin and/or cytokines (1,19). The inducibleThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.NO sy...

Cartilage glycosaminoglycan (GAG) synthesis and composition, upon which its structural integrity depends, varies with age, is modified by anabolic and catabolic stimuli, and is regulated by UDP-glucuronate availability. However, how such stimuli, prototypically represented by transforming growth factor-␤1 (TGF-␤1) and IL-1␣, modify GAG synthesis during aging of normal human articular cartilage is not known. Using explants, we show that chondroitin sulfate (CS):total GAG ratios decrease, whereas C6S:C4S ratios increase with cartilage maturation, and that chondrocytes in the cartilage mid-zone, but not the superficial or deep zones, exhibit uridine 5-diphosphoglucose dehydrogenase (UDPGD) activity, which is also increased in mature cartilage. We also show that IL-1␣ treatment reduces both total GAG and CS synthesis, decreases C6S:C4S ratios (less C6S), but fails to modify chondrocyte UDPGD activity at all ages. On the other hand, TGF-␤1 increases total GAG synthesis in immature, but not mature, cartilage (stimulates CS but not non-CS), age-independently decreases C6S:C4S (more C4S), and increases chondrocyte UDPGD activity in a manner inversely correlated with age. Our findings show that TGF-␤1, but not IL-1␣, modifies matrix synthesis such that its composition more closely resembles "less mature" articular cartilage. These effects of TGF-␤1, which appear to be restricted to periods of skeletal immaturity, are closely associated although not necessarily mechanistically linked with increases in chondrocyte UD-PGD activity. The antianabolic effects of IL-1␣ are, on the other hand, likely to be independent of any direct modification in UDPGD activity and manifest equally in human cartilage of all ages.

Impaired olfaction is an early pre-motor symptom of Parkinson's disease. The neuropathology underlying olfactory dysfunction in Parkinson's disease is unknown, however α-synuclein accumulation/aggregation and altered neurogenesis might play a role. We characterized olfactory deficits in a transgenic mouse model of Parkinson's disease expressing human wild-type α-synuclein under the control of the mouse α-synuclein promoter. Preliminary clinical observations suggest that rasagiline, a monoamine oxidase-B inhibitor, improves olfaction in Parkinson's disease. We therefore examined whether rasagiline ameliorates olfactory deficits in this Parkinson's disease model and investigated the role of olfactory bulb neurogenesis. α-Synuclein mice were progressively impaired in their ability to detect odors, to discriminate between odors, and exhibited alterations in short-term olfactory memory. Rasagiline treatment rescued odor detection and odor discrimination abilities. However, rasagiline did not affect short-term olfactory memory. Finally, olfactory changes were not coupled to alterations in olfactory bulb neurogenesis. We conclude that rasagiline reverses select olfactory deficits in a transgenic mouse model of Parkinson's disease. The findings correlate with preliminary clinical observations suggesting that rasagiline ameliorates olfactory deficits in Parkinson's disease.

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